Films capable of being transformed into ferroelectric materials have been investigated for their use in ICs due to their high remanent polarization (2P.sub.r) characteristics and long term storage reliability. Various techniques, such as sol-gel, chemical vapor deposition (CVD), sputtering, pulsed laser deposition (PLD), and evaporation, have been developed for depositing such films on a substrate.
CVD techniques, however, are preferred for large scale integration applications since as such techniques deposit conformal films at small design rules, such as .ltoreq.0.5 .mu.m. CVD techniques also provide other advantages, such as good film uniformity, high film density, convenient and reliable composition control, high throughput, and low cost.
Conventional CVD techniques include introducing precursors under appropriate process conditions into a reaction chamber. The deposition temperature is between about 450-700.degree. C. A reaction occurs, thereby depositing a film on a substrate. The as-deposited film is typically not a ferroelectric film. In some cases the as-deposited film may show poor ferroelectric characteristics, that is, low remanent polarization. An anneal, referred to as a "ferro-anneal," is often required to convert the as-deposited film into the ferroelectric film with 2P.sub.r or to improve the film's 2P.sub.r.
The ferro-anneal needed to transform an as-deposited film formed by conventional CVD techniques into a ferroelectric film consumes a relatively high thermal budget. Typically, the ferro-anneal is carried out at 700-800.degree. C. for about 1 hour. The high thermal budget is undesirable as it can result in the diffusion of one or more mobile elements from the as-deposited film into the substrate. For example, bismuth (Bi) atoms in Bi containing films are very mobile at high temperatures. Diffusion of mobile atoms into the substrate can adversely impact performance or functionality of the IC. Additionally, the high thermal budget combined with the oxidizing ambient of the anneal causes excessive oxidation. Excessive oxidation, particularly in the conductive materials such as the contact plug or plug, disrupts electrical conductivity between devices such as a capacitor and a transistor of a memory cell. Excessive oxidation may also blur the doping profile of, for example, the transistors.
In view of the foregoing discussion, it is desirable to provide an improved technique for forming a ferroelectric material which consumes a lower thermal budget than conventional techniques.